It's been a decade since The Office appeared on our TV screens. The story of daily grind in a Slough paper merchants was so realistic that when I stumbled across it on BBC2 one night it took me a minute to realise that it wasn't a documentary.

That revelation for me is something I'll always remember because I laughed a lot at a time when laughter in my life was a thin on the ground.

The show went on to become one of the most successful British comedies of all time, but for me its most notable aspect was the casting director's decision to hire the disabled actor Julie Fernandez.

Long before disability was a campaigning issue for me I'd found actors playing disabled characters embarrassing. Mimicking disabled people had been pounced on and swiftly dealt with when I was growing up. Yet at drama school this was embraced. To me playing disabled, when not disabled, was as incongruous as being asked to black up. I can't imagine people calling a performance under those circumstances brave or moving or groundbreaking, but there we were acting disabled yet simultaneously being told to find the truth in performance.

I hope that my daughter Lizzy, an actor with Asperger's syndrome, will have the same opportunities as any other performer but full representation of disabled people is uncommon in any profession, let alone television or broadcasting.

In advertising, drama series, sitcoms, soap operas or comedy panel shows, disabled performers are notably absent. There are a few disabled characters but fully inclusive casting is not routine. And this is despite there being more than 250 disabled members of Equity, the actors union in the UK.

There are some who say that things are getting better for disabled performers now that broadcasters have diversity departments, but the change is happening so slowly as to be imperceptible to the naked eye. The only place where you will find disabled people routinely featured is in documentaries; but in these there seems to be a demand for a type of misery heavy portrayals of disabled "victims" or "burdened" carers.

Widen the picture and there is even less representation. Why can't kids modeling clothes in adverts have Down's syndrome, newscasters be wheelchair users, and continuity voices be reading brail? It'sa question that many seem unwilling or unable to answer as they continue to cast predominantly white, non-disabled, beautiful, thin people of average height. Couldn't it be argued that to push any one of us into marginalised shadow simply draws the bigots into the mainstream light?

I'm not suggesting an actor be cast just because he or she is disabled, no actor wants be cast for anything other than skill. I just wonder how many disabled people were invited to any casting sessions in the UK in the last seven days.

Greater representation in every aspect of life reduces stigma borne out of ignorance and leads us away from the rising levels of hateful abuse which disabled people experience as a matter of course.

Ricky Gervais and Stephen Merchant produce projects which tackle our culture of discrimination and ignorance about difference, and they should receive more credit for highlighting these issues than they do. They projects are imbued with a light touch and a sense of humour which stems from a positive place. Their new series, Life's too short, stars Warwick Davies playing a twisted version of himself. It will tweak the cringe reflex that affects too many people when they encounter diversity.

People identified with The Office because they recognised and related to the people portrayed, who were telling the story of our lives. It's such a shame that so many of the programme makers who tried to emulate the show's success ignored the one aspect which bears repetition widely: authentic casting.

• Nicky Clark is a disability rights campaigner and mother to two children with disabilities. She leads two national campaigns Don't Play Me, Pay Me calling for inclusive representation of disabled people in the entertainment and advertising industry and People Not Punchlines which works to eliminate comedy specifically targeting disabled people. She blogs at nickyclark.blogspot.com/